When you try the lig for the first time it is important to get it to take the the shape of the mouthpiece, even though it is pretty close, typically.

If the ligature appears to be to small for your mouthpiece, check to see if the wires are contacting the sides of your mouthpiece. If there is contact, you may open this up using your thumb and
index finger to squeeze the reed pressure plate toward the barrels to widen the space between the wires and the mouthpiece sides. Then, a) Using an old unusable reed, position the reed and slip the lig
over so that the leading edge of the pressure plate is approx 1/16" to the rear of the mouthpiece window opening. Marking the old reed will make this easier to do to avoid having to flip the reed out
of the way to see the mouthpiece window.

b) Tighten the lig and if needed, massage the wires on the sides into conformity with the mouthpiece. Tighten some more. Tighten
somewhat more than normal but do not overdo it. Now the lig has the correct shape. Discard the old reed.

c) Each time you install a new reed, take particular care to position
it properly and then tighten the lig a half turn more than normal. This dents the reed with the 2 parallel ridges under the pressure plate.

d) Back off to a normal pressure.

On each subsequent installation of that reed, the ridges will find the depressions in the reed and make positioning a snap. The heel of the reed will be located where it belongs and will not
wander around as you adjust the tip as can happen with flexible (synthetic and leather) ligatures.